Problem: LESS file imports are added to BundleResponse.Files collection

First of all let me thank you for this great work. I finally managed to replace
dotLess with BundleTransformer, everything works, except one thing, which leads to massive problems:

I use BundleTransformer in a multi-tenant environment, where different stylesheets must be served on a tenant base, because each tenant can manage their own sets of LESS variables in the database. I've overwritten
Bundle.GetCacheKey() (among others) to vary cache keys by tenants successfully. When stylesheets for the
first tenant are processed, everything works like a charm, but once a
second tenant makes a request, the requested Bundle suddenly contains all imports in addition to my parent LESS files (in the sum I have 60 imports, pretty much ;-))

I suspect TransformerBase.ConfigureBundleResponse() to be responsible for this but am not sure. However, a quick look at the code reveals that all imports (dependencies) are pushed into
Bundle.Files, which unfortunately makes this otherwise wonderful project unusable in my special environment.

Currently the Microsoft ASP.NET Web Optimization Framework do not gives us opportunities to directly manage the cache dependencies of bundle, and therefore we can only add @imports (as well as other types of file dependencies) to the
BundleResponse.Files property. In fact, the BundleResponse.Files property contains only references.

Actually, I don't quite understand how working your solution. Let me just say one, that the Bundle Transformer work with file system via the virtual path provider, which can be specified by using the
BundleTable.VirtualPathProvider property. You need to write your own implementation of the
VirtualPathProvider class.

I already make heavy use of VirtualPathProvider (implemented my own to load LESS files from database and create custom
CacheDependeny instances).

In the meantime I managed to clean out BundleResponse.Files by removing all LESS imports within my overridden
Bundle.UpdateCache(). But one problem remains:
Enable custom cache key creation for debug mode. I don't like the idea of implementing my own HttpHandler, this would lead to much redundant code.

If you could give me a hint about whether you plan to implement the issue, I would wait for it, otherwise I will implement a custom HttpHandler :-(